Peter Gamma from Www.petergamma.org has reviewed about this on www.petergamma.org, especially in this review paper: But Peter Charlton shows us the 2023 wearable photoplethysmography roadmap in a paper: https://iopscience.iop.org/article/10.1088/1361-6579/acead2 Peter Charlton is a Biomedical Engineer specialising in signal processing for wearables. Many of Peter’s latest conference presentations and seminars are available on his YouTube channel, …